The common Dharani and pronunciation of Ksitigarbha Bodhisattva are as follows.

The mantra of annihilation of fixed karma (the seal of Ksitigarbha Bodhisattva’s Dharmakaya): Om pramar dani svaha (Volume 6 of "Dharani Sutra Collection"); phonetic notation: Om pra mar dani svaha.

Ksitigarbha Bodhisattva's mantra: Om He He He Wei Suo Mo Yi Sha He ("The Great Vairocana Buddha's Divine Transformation Blessing Sutra, Lotus Embryo Collection, Compassionate Birth Mandala, Vast Achievement Ritual" volume 2); Phonetic notation: Om ha-ha-ha vismaya svaha.

Ksitigarbha Bodhisattva’s mantra: Nanmo Sanmanduobo? Namhahahasutanushaha (Virochana’s Divine Transformation and Blessing Sutra for Becoming a Buddha, Volume 2); phonetic notation: na mah sa ma nta bu ddha nam ha ha ha su ta nu sva ha (Volume 1 of "The Sanskrit Mantra of the Embryo Storehouse").

For reference~